1. Field of the Invention
The present invention generally relates to lighting systems involving light pipes, and more particularly, to near field lenses that collect and direct light from light sources and send such light into light pipes.
2. Description of Related Art
Light-emitting diode (LED) light pipes are increasingly finding applications for automotive signal lamps because of their aesthetic look and signature differentiation between vehicle lines. Typical LED light pipes have diameters between five and twenty millimeters with vast variations in length. Styling themes demand light pipes having oddly curved shapes, which are optically challenging to design. This increase in shape complexity of the light pipes makes both the optical design and manufacturing of the light pipe very difficult. Light pipes that have complex shapes typically have lower optical efficiency and require high power LEDs to meet the Federal Motor Vehicle Safety Standards (FMVSS) beam pattern regulations.
Since most of the high powered LEDs emanate light in a nearly Lambertian pattern (radially along a hemisphere), and since the light pipe diameters are so small, the light entering the light pipe is typically only between 10-20% of the source light. This amount of light is insufficient for many designs.
Typical solutions to this problem are a reduction in the length of the light pipe, a reduction in the complexity of the light pipe, or additional light from the source. For example, very high powered LEDs or other light sources, such as mini halogen bulbs with elliptic reflectors, may be used in order to promulgate adequate light into the light pipe. Likewise, complex light delivery system using bulbs, reflectors, glass rods, and optical fibers may be used to try to promulgate adequate light into the light pipe. Furthermore, the LED light output may be increased via binning and advanced electronics.
However, if light pipe lengths or diameters need to be reduced, or if additional light needs to be added, cost and customer satisfaction may be impacted. Therefore, an optical device may be used to improve the amount of light entering the light pipe. The optical device, for example, a near-field lens, collects the light emitted by the LED source and sends it to the light pipe entrance. However, since many of the high powered LEDs come with optics (a “dome”) above the chip with 5-8 mm diameters, it is difficult to design an optical device that will accommodate both the LED optic and a light pipe having a small diameter (5-10 mm).
In view of the above, it is apparent that there is a need to more efficiently utilize the source light from an LED or other light source having non-planar surface optics.